This Qt App can control the volume of a 5.1 surround sound system in Windows OS for each channel: Front, Rear, Subwoofer, Center, Side (mmsys.cpl).
Used COM and WASAPI without third party libs.
COM Interfaces: IMMDevice, IMMDeviceEnumerator, IDeviceTopology, IConnector, IPart, IAudioVolumeLevel.
Note
These formulas convert percent->db and db->percent
https://sengpielaudio.com/calculator-thd.htm
percent->db: valueDB = 20 * lg(valueSliderFloat/100)
db->percent: valuePercent = 10^(valueDB/20) * 100
Find GUID/KSNODE in Ksmedia.h and see what interface is possible init:
https://learn.microsoft.com/en-us/windows/win32/api/devicetopology/nf-devicetopology-ipart-getsubtype
- 02b223c0-c557-11d0-8a2b-00a0c9255ac1 ->
KSNODETYPE_MUTE - dff21ce1-f70f-11d0-b917-00a0c9223196 ->
KSNODETYPE_SPEAKER - 3a5acc00-c557-11d0-8a2b-00a0c9255ac1 ->
KSNODETYPE_VOLUME - da441a60-c556-11d0-8a2b-00a0c9255ac1 ->
KSNODETYPE_SUM - 6994ad04-93ef-11d0-a3cc-00a0c9223196 ->
KSCATEGORY_AUDIO